Solid propellant grains having many varieties of shapes, sizes, and formulations have been manufactured for civilian and military uses. Since the grain consists of many chemicals, it is essential that a stable condition exists, and the grain undergoes only minimum change or deterioration of its characteristics when the grain is to be stored for a period of time. The period of time for which propellant grains can be stored until they become unsafe to use will vary according to the environmental conditions to which the grains are exposed. It is essential that propellant grains be checked or monitored during storage to determine what changes may have occurred since the grains were manufactured.
Various methods of non-destructive testing have been used in monitoring propellant grains. Test firings of samplings of propellant grains that have been stored under various conditions have been accomplished to detect changes or to determine reliability. The test firing procedure is both expensive and time consuming. Non-destructive testing is, by far, the preferred if it provides the information necessary for the assessment of the propellant's condition. In the past, the means for determining the mechanical behavior of solid propellants under specified load conditions have been limited since a stress-strain law that describes such behavior did not exist. One means for assessing mechanical behavior has been the analog computer circuits; however, these computer circuits that have been synthesized to describe mechanical behavior or response are too complicated for efficient use.
Desirable would be a means for assessing mechanical behavior by non-destructive testing of solid propellant grains during storage.
The primary objective of this invention is to provide a simple procedure to establish whether a propellant grain has not undergone significant deterioration in its mechanical properties which would make it unsafe to fire.
Therefore an object of this invention is to provide a means for assessing mechanical properties of solid propellant grains.
Another object of this invention is to provide a solid propellant grain that has sufficient electrical conductivity to permit conductance measurements which serve as a means of assessing conditions of a solid propellant grain that can be correlated with mechanical properties and mechanical behavior under load conditions.